Fed up with constant visits by police and soldiers since the military coup on May 22, academics and activists turned up at an army unit in Chiang Mai yesterday to demand an end to harassment by the junta.

The group of 16, mostly academics from Chiang Mai University, urged the army to respect their freedom of expression and formally inform individuals when it was summoning them for "talks".

Unlike in Bangkok, where the junta has publicised names of people it intended to summon and possibly detain, the picture outside the capital is a lot murkier.

In Chiang Mai, the intellectual capital of northern Thailand and stronghold of the ousted government, academics have received phone calls summoning them to army quarters, or visits from police asking for details of their colleagues. Others have had their properties searched by troops.

In a country where enforced disappearances are not uncommon, this has made them fear for their safety.

Anthropologist Anan Ganjanapan told The Straits Times: "We want to make sure we don't have to hide any more. We didn't do anything wrong."

Since taking power more than a week ago, the Thai junta has muzzled the media and clamped down on dissent. On Sunday, it locked down a part of central Bangkok to prevent any anti-coup protest from taking place.

The military warned the media against publishing interviews with academics and analysts that "confuse the public", chilling the normally vibrant discussion.

In recent days, it has cracked down in the north-eastern province of Khon Kaen, arresting over 3,400 people and recovering a large number of weapons, including several hundred guns.

The sweep focused on illegal rackets like drugs and gambling, often run by local mafia with politicians and police complicit in the act. But Khon Kaen is also a stronghold of the ousted government.

Closer to Bangkok in Chonburi province, a large cache of 180 M67 hand grenades and 27 rocket-propelled grenades were found by locals in a banana grove yesterday. Police said they had most likely been dumped there by people afraid of being caught in the army's ongoing security cleanup.

Academics officially summoned by the junta so far include prominent historian Charnvit Kasetsiri and Thammasat University associate law professor Worachet Pakeerut, a founder of the legal advocacy group Nitirat which has criticised both the ousted government and the military.

Observers point out that many of those called up in one way or another supported efforts to amend the lese majeste law, which metes out jail sentences for insults against the monarchy.

Junta leader and army chief Prayuth Chan-ocha says the restrictions are temporary but necessary to stabilise a country riven by nearly a decade of political conflict. He has set a roughly 15- month timeframe for fresh elections to be held.

Critics argue that the junta is using martial law to remove the imprint of Thaksin Shinawatra, the billionaire turned premier who was overthrown in a military coup in 2006. Although he lives abroad to evade a jail term for graft, voters have repeatedly returned his allies to power - to the consternation of the royalist establishment and urban middle class.

In the north and north-east, the military temporarily detained leaders of the pro-Thaksin "red shirt" movement to neutralise opposition to the coup. The junta has also blocked the webpage of Midnight University, a website of scholarly articles set up by Chiang Mai intellectuals.

Yesterday's meeting between academics and the military in Chiang Mai was cordial, although it was the first time some intellectuals had come out of hiding to face the troops hunting for them.

Addressing the academics' fears afterwards, local army commander Sarayuth Rungsri told reporters: "You don't have to be afraid if you didn't do anything wrong."

Chiang Mai University sociologist Wattana Sugunnasil told The Straits Times: "I get the sense of they were saying, 'we've got to be careful'."